Enantioselective accumulation of α-hexachlorocyclohexane in northern fur seals and double crested cormorants:: Effects of biological and ecological factors in the higher trophic levels

Tissues of northern fur seals (Callorhinus ursinus) from the Pacific coast of Japan and double-crested cormorants (Phalacrocorax auritus) from the Great Lakes were analyzed in order to explore the enantioselective accumulation of alpha-hexachlorocyclohexane (HCH). The effects of biological and ecological factors such as species, tissue, sex, age, feeding habit, and habitat, which may be attributable to the differences in accumulation between enantiomers, were also investigated. The enantiomeric ratios (ERs) of (+)-/(-)-alpha-HCH in fat tissue of female fur seals, composed of different age groups, collected in 1986 (1.58 +/- 0.25) exhibited greater values than those in abiotic and lower trophic levels previously reported. No age trend of ERs was found in female northern fur seals. There appeared to be a temporal transition of ERs in adult female northern fur seals collected in 1971-1988. Regression analysis showed a significant relationship between ERs and feeding habits (p = 0.003). Analysis of breast muscle of double-crested cormorants exhibited no sex difference in ERs. ERs (1.26 +/- 0.13) in cormorants from Lake Michigan were significantly higher than those (1.01 +/- 0.18) from Lake Superior (p = 0.002), suggesting the effects of factors such as feeding habit and habitat. Enantiomeric accumulation in the body of double-crested cormorants was tissue-specific. No age trend of ERs was seen in breast muscle of cormorants. The result implies that sexual maturity, aging and breeding activities are less effective for changing ERs. The ERs in higher trophic animals could be influenced by species-specific metabolism and transport process in the body as biological factors and by feeding habit and habitat as ecological factors.